Chemical mechanical polishing for forming a shallow trench isolation structure

Abstract

A method of chemical-mechanical polishing for forming a shallow trench isolation is disclosed. A substrate having a number of active regions, including a number of relatively large active regions and a number of relatively small active regions, is provided. The method comprises the following steps. A silicon nitride layer on the substrate is first formed. A number of shallow trenches are formed between the active regions. An oxide layer is formed over the substrate, so that the shallow trenches are filled with the oxide layer. A partial reverse active mask is formed on the oxide layer. The partial reverse active mask has an opening at a central part of each relatively large active region. The opening exposes a portion of the oxide layer. The opening has at least a dummy pattern. The oxide layer on the central part of each large active region is removed to expose the silicon nitride layer. The partial reverse active mask is removed. The oxide layer is planarized to expose the silicon nitride layer.

What is claimed is: 
     
       1. A method of chemical-mechanical polishing for forming a shallow trench isolation, wherein a substrate having a plurality of active regions, including a plurality of relatively large active regions and a plurality of relatively small active regions, is provided, comprising:
 forming a silicon nitride layer on the substrate; 
 forming a plurality of shallow trenches between the active regions; 
 forming an oxide layer over the substrate, so that the shallow trenches are filled therewith, 
 forming a partial reverse active mask on the oxide layer, wherein the partial reverse active mask has an opening at a central part of each relatively large active region, wherein the opening exposes a portion of the oxide layer, and wherein the opening has at least a dummy pattern; 
 removing the oxide layer on the central part of each large active region to expose the silicon nitride layer therewithin; 
 removing the partial reverse active mask; and 
 planarizing the oxide layer to expose the silicon nitride layer. 
 
     
     
       2. A method as claimed in  claim 1 , wherein the shallow trenches are formed by photolithography and etching. 
     
     
       3. A method as claimed in  claim 1 , wherein the oxide layer is formed by high density plasma chemical vapor deposition. 
     
     
       4. A method as claimed in  claim 1 , wherein the exposed portion of the oxide layer is removed by anisotropic etching. 
     
     
       5. A method as claimed in  claim 4 , wherein the exposed portion of the oxide layer is removed, using the silicon nitride layer as an etching stop layer. 
     
     
       6. A method as claimed in  claim 1 , wherein the oxide layer is planarized by chemical mechanical polishing. 
     
     
       7. A method of forming a partial reverse active mask pattern, applied in fabricating shallow trench isolation, wherein the method comprises:
 providing a mask pattern, wherein the mask pattern comprises a plurality of relatively large active region patterns and a plurality of relatively small active region patterns; 
 shrinking the relatively large active region patterns and the relatively small active region patterns until the relatively small active region patterns disappear and the relatively large active region patterns become a remaining relatively large active region patterns; and 
 enlarging the remaining relatively large active region patterns so that the remaining relatively large active region patterns are substantially smaller than original profiles of the relatively large active regions and each of the relatively large active region patterns has at least one dummy pattern. 
 
     
     
       8. A method as claimed in  claim 7 , wherein in said step of shrinking the relatively large active region patterns and the relatively small active patterns, a shrinking size is about between 0.5 μm and 2 μm. 
     
     
       9. A method as claimed in  claim 7 , wherein in said step of enlarging the remaining relatively large active region patterns, an enlarging size is about between 0.2 μm and 2 μm. 
     
     
       10. A method as claimed in  claim 7 , wherein an enlarging size in said step of enlarging the remaining relatively large active region patterns is substantially smaller than a shrinking size in said step of shrinking the relatively large active region patterns and the relatively small active patterns.